1. Field of the Invention
The present invention relates to a linear motor used for conveying objects or a linear motion devices in industry, and in particular, relates to a linear magnetization mover motor due to linear force resulting from the interaction between a magnetostatic induction element and electromagnetic coils.
2. Related Art
According to "The Present State and the applied Technology of the Linear Electromagnetic Driving System" that is a technical report of the Institute of Electrical Engineers of Japan [Section 2], No. 314, linear electromagnetic actuators classify two groups; linear motors obtainable by developing rotary motors cut open in a straight line; and the other is linear actuators, which are called linear motion oscillators, and is limited to a certain extent of motion in itself. According to the definition, the linear motors, i.e., linear induction motors, linear synchronous motors, linear pulse motors, linear direct current motors, or linear hybrid motors that are combinations of other types of linear motors, or the like, have a linear driving force interactive between a current filament and a traveling magnetic field, instead of the rotating field at the rotating machines. The linear actuators, such as electromagnetic pumps or the like, which generate linear attractive force within a limited range of motion are not included in the linear motors. According to other documents, an electromagnetic gun for accelerating a projectile under Fleming's left hand rule is also categorized as an apparatus for creating linear propulsive and attractive force.
FIG. 10 shows an example of a conventional magnetic leakage type of a linear electromagnetic solenoid actuator having an electromagnetic air-core coil 102 and a movable plunger 101, which is limited to a certain extent of motion in itself. Such an actuator is described on page 27 of "Linear Motor and Their Application" which is edited by the Institutes of Electrical Engineers and published by Ohmsha LTD.
The above linear electromagnetic actuators use electromagnetic attraction or repulsive force resulting from the interaction between a current filament (or a magnetic element) and a magnetic field.
In the linear motors according to the present invention wherein electromagnetic air-core coil, ferromagnetic core coil or the like and movable element are employed, magnetizable materials made by an induced magnetization from a magnetostatic field is used instead of the current or the magnet that are used in the linear electromagnetic actuators described above.
The technical report of Electrical Society [Section 2], No. 314 discloses a linear oscillatory actuator which is a linear actuator exerting linear reciprocation on a movable member by electrical input without using any converter; and a linear electromagnetic solenoid which is a component giving linear motion directly to a movable iron core by the electromagnetic force which is exerted on an exciting coil by application of voltage. Japanese Utility Model Application Kokai (Laid-Open) No. 50-79953 discloses a digital solenoid comprising a movable iron core which can be linearly moved through a cylindrical exciting coil by exciting the coil. "Linear Motor for Industry", edited by Hajime Yamada and published by Kogyo chosakai Publishing Company, Limited, discloses a linear digital actuator. Each of the above-described actuators, however, has a limited stroke, therefore, is different from the present invention that is a linear motor with electromagnetic air-core coil and has a magnetic induction element that is an electromagnetic air-core coil according to which enables continuous linear propulsion of objects.
Since the conventional linear motor is obtained by developing a rotary motor cut open in a straight line, in a direction of motion thrust, propulsion force and traction force result from interaction between a current filament and traveling magnetic field intensity. The forces have the direction mutually perpendicular to the traveling magnetic field and the current. FIG. 11 schematically shows attraction and repulsive forces acting between the mover (a magnet or an electromagnetic coil) 111 and ground coils 112-A, 112-B, 112-C, . . . , and 112-N, according to a conventional construction. As shown in the figure, when the mover of a current loop (or magnetic poles) and the other current loop (the magnetic poles of magnets) face to each other, the attractive force exerted on the mover is zero to the direction of thrust and propulsion, and when the half overlapping condition both the current loop and the other current loop, the mover receives a largest transversal force. Therefore, the linear driving force exerted on the mover varies as the object travels along the track or the magnitude of traveling magnetic field. It is possible to create a continuous magnetic field by disposing the magnets to overlap with one another. However, this solution will make necessary a complex structure.
The magnetic field that issues from the excitation of electromagnetic coil has the maximum intensity at the center of the coil and the intensity gradually decreases according to the distance from the center. Therefore, the closer to the center of the coil, the more intensive the magnetic field. Accordingly, it is necessary to locate interacting magnets, the magnetostatic magnet and magnet (or a current filament), as close as possible to each other to economize the magnetic energy. However, according to the conventional linear motor, the mover (or a magnet, current filament) is not always located where magnetic field has the greatest magnetic intensity as clearly shown in FIG. 11. Therefore, such a conventional structure requires a large electric current to obtain necessary attractive force
The driving force is produced by the vector product of the magnetic field intensity and the current intensity of the mover. Other problems in conventional linear motors are that a high-powered permanent magnet, an exciting power supply and coils for producing a high-powered electromagnet, a cooling device, a power supply for cooling, and an exciting circuit therefor is required.